let _Vue = null;
export default class VueRouter {
  static install(Vue) {
    // 1、判断当前插件是否已经被安装
    if (VueRouter.install.installed) return;
    VueRouter.install.installed = true;
    // 2、把Vue构造函数记录到全局变量
    _Vue = Vue;
    // 3、把创建Vue实例传入的router对象注入到Vue实例上
    _Vue.mixin({
      beforeCreate() {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router;
          this.$options.router.init();
        }
      }
    });
  }

  constructor(options) {
    this.options = options;
    this.routeMap = {};
    this.data = _Vue.observable({
      current: '/'
    });
  }

  init() {
    const mode = this.options.mode;
    this.createRouteMap();
    this.initComponents(_Vue, mode);
    this.initEvent();
  }

  createRouteMap() {
    // 遍历所有路由规则，并解析成键值对的形式,存储到routerMap中
    this.options.routes.forEach((route) => {
      this.routeMap[route.path] = route.component;
    });
  }

  initComponents(Vue, mode) {
    this['init' + mode + 'Components'](Vue);
  }

  inithistoryComponents(Vue) {
    Vue.component('router-link', {
      props: {
        to: String
      },
      render(h) {
        return h(
          'a',
          {
            attrs: {
              href: this.to
            },
            on: {
              click: this.clickHandler
            }
          },
          [this.$slots.default]
        );
      },
      methods: {
        clickHandler(e) {
          history.pushState([], '', this.to);
          this.$router.data.current = this.to;
          e.preventDefault();
        }
      }
    });
    const self = this;
    Vue.component('router-view', {
      render(h) {
        const component = self.routeMap[self.data.current]
          ? self.routeMap[self.data.current]
          : self.routeMap['*'];
        return h(component);
      }
    });
  }

  inithashComponents(Vue) {
    Vue.component('router-link', {
      props: {
        to: String
      },
      render(h) {
        return h(
          'a',
          {
            attrs: {
              href: '#' + this.to
            },
            on: {
              click: this.clickHandler
            }
          },
          [this.$slots.default]
        );
      },
      methods: {
        clickHandler(e) {
          window.location.hash = '#' + this.to;
          console.log(this.$router.data.current);
          this.$router.data.current = this.to;
          e.preventDefault();
        }
      }
    });
    const self = this;
    Vue.component('router-view', {
      render(h) {
        const component = self.routeMap[self.data.current]
          ? self.routeMap[self.data.current]
          : self.routeMap['*'];
        return h(component);
      }
    });
  }

  initEvent() {
    window.addEventListener('popstate', () => {
      this.data.current = window.location.pathname;
    });
    window.addEventListener('hashchange', () => {
      this.data.current = window.location.hash.slice(1);
    });
  }
}
